PROJECT SUMMARY/ABSTRACT Using a bioinformatics analysis, we have identified viral insulin/IGF1-like peptides (VILPs) in the genomes of four different, but related, viruses. Although these viruses were isolated from fish, assessment of the VILPs in a phylogenetic context showed that VILPs are equally well-related to humans and other species as to fish insulins/IGFs. Nothing is known about how these VILPs might interact with mammalian insulin or IGF-1 receptors, and about the potential impact of these viruses and their insulin-like peptides in terms of diabetes pathogenesis or organismal/tumor growth, all processes highly regulated by mammalian insulins and insulin- like growth factors. The overarching goal of this proposal is to functionally characterize the VILPs, define their mechanism of action, understand their potency and determine if they affect mammalian pathophysiology. The central hypothesis is that VILPs are new members of the insulin super-family that can interact with mammalian insulin and IGF-1 receptors and activate insulin/IGF-1 signaling thereby altering cellular metabolism, gene expression and cell proliferation. This hypothesis has been formulated on the basis of exciting preliminary data produced in the applicant's laboratory. The rationale for the proposed research is that understanding the functions of VILPs on mammalian cells has the potential to translate into better understanding of fundamental mechanisms and early origins of insulin/IGF-1 signaling, and how these peptides may be involved in not only viral diseases, but also type 2 diabetes (T2D), type 1 diabetes (T1D) and conditions of tumor growth. Together these disorders affect millions of people in this country and worldwide. Guided by our preliminary data, this hypothesis will be tested by pursuing two specific aims: 1) Determine the molecular mechanisms of VILP action as novel insulin and IGF-1 receptor ligands and 2) explore the pathophysiologic effects of VILPs on glucose homeostasis and cell growth in mice. Under Aim 1, functional characterization of VILPs will be performed using human, rodent and fish cells. In addition to exogenous effects, VILPs will be cloned into mammalian cells and their effects as endogenous ligands will be assessed. With collaborators, the NMR structures of VILPs will be determined and compared to their mammalian counterparts. Under Aim 2, we will characterize the acute and chronic effects of VILPs in vivo. To this end, VILP genes will be transferred to the liver of mice using an adeno-associated viral vector system. The local effects of VILP overexpression on liver and their systemic effects on the body will be determined This approach is innovative since it will be the first exploration of VILP action and their impact on insulin signaling, metabolism, gene expression and growth. The proposed research is significant, because it will be the first study that advances our understanding of VILP function and their potential impact on human disease. Ultimately, such knowledge has the potential to help us not only understand the role of these molecules, but to better understand insulin/IGF-1 action overall, which may be useful in designing new, unique insulin analogs.